Liquid crystal panel structures containing functionalized graphene layers and methods of preparing functionalized graphene layers

ABSTRACT

A method for preparing a functionalized graphene layer is provided. The method utilizes superiority of transparent conductivity of the graphene and modifiability of the graphene surface to endow the graphene with an effect of liquid crystal molecule alignment. Thus, the functionalized graphene layer provides both transparent conductivity and liquid crystal alignment, and an alignment process that subsequently uses an alignment material is not necessary.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional application of co-pending U.S. patent applicationSer. No. 15/112,432, filed on Jul. 19, 2016, which is a national stageof PCT Application No. PCT/CN2016/085794, filed on Jun. 15, 2016,claiming foreign priority of Chinese Patent Application No.201610340789.4, filed on May 20, 2016.

FIELD OF THE INVENTION

The present application relates to display technical fields, especiallyto a liquid crystal panel containing a functionalized graphene layer anda method of preparing a functionalized graphene layer.

BACKGROUND OF THE INVENTION

A thin film transistor liquid crystal display (LCD) device has manyadvantages of thin body, power saving, no radiation, so it obtains widerange application. Most of the liquid crystal devices in current marketare backlight type liquid crystal display, which includes a liquidcrystal display panel and a backlight module. The working principle ofthe liquid crystal display panel is: placing liquid crystal molecules intwo parallel glass substrates, which have many vertical and horizontalfine wires between the two glass substrates; controlling the liquidcrystal molecules to change direction by energizing or not energizing;and refracting light of the backlight module to produce frames.

Generally, the liquid crystal display panel is consisting of a colorfilter (CF) substrate, a thin film transistor (TFT) substrate, liquidcrystal (LC) interposed between the CF substrate and the TFT substrate,and a sealant. In TFT-LCD, classifications based on operation modes ofthe liquid crystal have phase change (PC), twisted nematic (TN), supertwisted nematic (STN), vertical alignment (VA), and in plane switching(IPS), etc. For the purpose of the common VA display mode, it is neededthat a transparent conductive film is simultaneously and respectivelydisposed on a side, facing the liquid crystal layer, of the CF substrateand the TFT substrate, a main function of the transparent conductivefilm is to form an electric field between the CF substrate and the TFTsubstrate, and to drive deflection of the liquid crystal molecules, soas to achieve bright and dark display.

Currently, the conventional transparent conductive film is indium tinoxide (ITO) film prepared by methods of physical vapor deposition (PVD).Additionally, after the transparent conductive films on the TFTsubstrate and the CF substrate are formed, an alignment film of tens tohundreds nanometers thickness is usually coated or printed thereon, whenliquid crystal (LC) is contacted with the alignment film, LC can beallowed to form a pre-inclination angle at a certain direction, so as toprovide a load angle for the liquid crystal molecules (a size of thepre-inclination angle has an important influence on driving voltage,contrast ratio, response time, viewing angle of TFT-LCD).

A material of the alignment film is usually chosen polyimide (PI)material, which is mainly classified as rubbing alignment type PImaterial and an optical alignment type PI material; however, no matterwhat the type of alignment material is, it has its own shortcoming.

Graphene has excellent transparent conductive and mechanicalperformances, there are many patents disclose that the graphene is usedas transparent conductive films. Methods of forming the transparentconductive graphene layer can be chemical vapor deposition (CVD),CVD-transfer, graphene solution printing, and graphene oxide solutionprinting-reduction. However, in such patents, the graphene is only usedas the transparent electrode layer; after that, it is still needed toperform material and process of the alignment film.

SUMMARY OF THE INVENTION

An aspect of the present application is to provide a liquid crystalpanel structure containing a functionalized graphene layer, thefunctionalized graphene layer thereof simultaneously plays effects oftransparent conductivity and liquid crystal alignment, an alignmentprocess that subsequently uses an alignment material is not necessary,the fabrication process and film structures of the liquid crystaldisplay panel are greatly simplified.

Another aspect of the present application is to provide a method ofpreparing a functionalized graphene layer, the method sufficientlyutilizes superiority of transparent conductivity of the graphene, andmodifiability of the graphene surface, to endow the graphene with aneffect of liquid crystal molecule alignment, the functionalized graphenelayer prepared thereby has transparency, conductivity and alignmentfunctions.

To achieve the above aspect, the present application provides a liquidcrystal panel structure containing a functionalized graphene layer,including oppositely disposed an upper substrate and a lower substrate,and a liquid crystal layer disposed between the upper substrate and thelower substrate;

a side of the upper substrate near the liquid crystal layer has afunctionalized graphene layer disposed thereon;

the functionalized graphene layer is a functionalized graphene film, thefunctionalized graphene film is a film of graphene surface grafted withliquid crystal vertical alignment molecules;

materials of the liquid crystal layer include liquid crystal molecules,liquid crystal vertical alignment molecules in materials of thefunctionalized graphene layer graft on the graphene surface, tovertically align the liquid crystal molecules in the liquid crystallayer.

A molecule structural formula of the liquid crystal vertical alignmentmolecules is

wherein R is

where m is an integer of 1-5 and n is an integer of 15-30.

Optionally, a side of the lower substrate near the liquid crystal layerhas a functionalized graphene layer disposed thereon, and a surface of aside of the functionalized graphene layer near the liquid crystal layerhas been rubbed, to provide a pre-inclination angle for the liquidcrystal molecules in the liquid crystal layer.

Optionally, an ITO electrode layer and an alignment film layer aresuccessively bottom up disposed on a side of the lower substrate nearthe liquid crystal layer, and the alignment film layer provides apre-inclination angle for the liquid crystal molecules in the liquidcrystal layer.

The upper substrate is a color film substrate, and the lower substrateis a TFT array substrate.

The present application further provides a method of preparing afunctionalized graphene film, including following steps:

Step 1, functionalizing a graphene oxide: preparing a graphene oxide byutilizing Hummer's method, reacting the obtained graphene oxide withliquid crystal vertical alignment molecules having liquid crystalalignment function, to graft the vertical alignment molecules on asurface of the graphene oxide, to obtain a functionalized grapheneoxide;

Step 2, forming a functionalized graphene oxide film: providing asolvent, mixing the functionalized graphene oxide obtained in Step 1with the solvent, and through a sonication, to obtain a uniformlydispersed functionalized graphene oxide dispersion; providing asubstrate, forming a functionalized graphene oxide film on the substrateby the functionalized graphene oxide dispersion; and

Step 3, reducing the functionalized graphene oxide: performing ahydrogen gas reduction treatment to the functionalized graphene oxidefilm obtained in Step 2, to obtain a material that is a functionalizedgraphene film of graphene surface grafted with liquid crystal verticalalignment molecules.

A molecule structural formula of the liquid crystal vertical alignmentmolecules is

wherein R is

where m is an integer of 1-5 and n is an integer of 15-30.

The solvent provided in Step 2 is a solvent of one or mixing more thanone of acetonitrile, acetone, tetrahydrofuran, N-methylpyrrolidone,water, acetone, ethanol, N, N-dimethylformamide, dichloromethane,chloroform, propanol, isopropanol, and ethylene glycol.

Step 3 further includes rubbing the obtained functionalized graphenefilm.

In Step 2, forming the functionalized graphene oxide film on thesubstrate by the functionalized graphene oxide dispersion is performedby a method of inkjet printing or transferring.

The present application further provides a method of preparing afunctionalized graphene film, including following steps:

Step 1, functionalizing a graphene oxide: preparing a graphene oxide byutilizing Hummer's method, reacting the obtained graphene oxide withliquid crystal vertical alignment molecules having liquid crystalalignment function, to graft the vertical alignment molecules on asurface of the graphene oxide, to obtain a functionalized grapheneoxide;

Step 2, forming a functionalized graphene oxide film: providing asolvent, mixing the functionalized graphene oxide obtained in Step 1with the solvent, and through a sonication, to obtain a uniformlydispersed functionalized graphene oxide dispersion; providing asubstrate, forming a functionalized graphene oxide film on the substrateby the functionalized graphene oxide dispersion; and

Step 3, reducing the functionalized graphene oxide: performing ahydrogen gas reduction treatment to the functionalized graphene oxidefilm obtained in Step 2, to obtain a material that is a functionalizedgraphene film of graphene surface grafted with liquid crystal verticalalignment molecules;

wherein a molecule structural formula of the liquid crystal verticalalignment molecules is

wherein R is

where m is an integer of 1-5 and n is an integer of 15-30; and

wherein the solvent provided in step 2 is a solvent of one or mixingmore than one of acetonitrile, acetone, tetrahydrofuran,N-methylpyrrolidone, water, acetone, ethanol, N, N-dimethylformamide,dichloromethane, chloroform, propanol, isopropanol, and ethylene glycol.

Advantages of the present application: in the liquid crystal panelstructure containing a functionalized graphene layer of the presentapplication, the functionalized graphene layer thereof simultaneouslyplays effects of transparent conductivity and liquid crystal alignment,an alignment process that subsequently uses an alignment material is notnecessary, the fabrication process and film structures of the liquidcrystal panel are greatly simplified. In the method of preparing thefunctionalized graphene layer of the present application, the grapheneoxide is firstly prepared by Hummer's method, by reacting the liquidcrystal vertical alignment molecules having liquid crystal alignmentfunction with functional groups on the graphene surface, thefunctionalized graphene oxide is obtained; then, the functionalizedgraphene oxide film is obtained by film-forming the functionalizedgraphene oxide; then other functional groups containing oxygen on thefunctionalized graphene oxide film are reduced to obtain the materialthat is the functionalized graphene film of graphene surface graftedwith liquid crystal vertical alignment molecules. The method ofpreparing the functionalized graphene layer of the present applicationsufficiently utilizes superiority of transparent conductivity of thegraphene, and modifiability of the graphene surface, to endow thegraphene with an effect of liquid crystal molecule alignment, thefunctionalized graphene layer prepared thereby has transparency,conductivity and alignment functions, and it will also play more obvioussuperiority in future flexible display and transparent display.

BRIEF DESCRIPTION OF THE DRAWINGS

The technical features and other advantages of the present applicationwill become more readily apparent to those ordinarily skilled in theart, by referring the following detailed description of embodiments ofthe present application in conjunction with the accompanying drawings.

In the accompanying drawings,

FIG. 1 schematically illustrates a structure of a liquid crystal panelcontaining functionalized graphene layer according to a first embodimentof the present application;

FIG. 2 schematically illustrates a structure of a liquid crystal panelcontaining functionalized graphene layer according to a secondembodiment of the present application;

FIG. 3 is a flowchart schematically illustrating a method of preparing afunctionalized graphene film of the present application;

FIG. 4 schematically illustrates a reaction of functionalizing thegraphene oxide in step 1 of the method of preparing the functionalizedgraphene film of the present application; and

FIG. 5 schematically illustrates a reaction of reducing thefunctionalized graphene oxide in step 3 of the method of preparing thefunctionalized graphene film of the present application.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In order to further clarify the technical means adopted in the presentapplication and the effects thereof, the preferable embodiments of thepresent application and the accompanying drawings thereof will be morespecifically described as follows.

Referring to FIG. 1, which schematically illustrates a structure of aliquid crystal panel containing functionalized graphene layer accordingto a first embodiment of the present application, the liquid crystalpanel structure containing functionalized graphene layer includesoppositely disposed an upper substrate 10 and a lower substrate 20, anda liquid crystal layer 30 disposed between the upper substrate 10 andthe lower substrate 20.

Specifically, a side of the upper substrate 10 near the liquid crystallayer 30 has a functionalized graphene layer 40 disposed thereon.

Specifically, the functionalized graphene layer 40 is a functionalizedgraphene film, and the functionalized graphene film is a film ofgraphene surface grafted with liquid crystal vertical alignmentmolecules.

Specifically, materials of the liquid crystal layer 30 include liquidcrystal molecules 31, liquid crystal vertical alignment molecules inmaterials of the functionalized graphene layer 40 graft on the graphenesurface, to vertically align the liquid crystal molecules 31 in theliquid crystal layer 30.

Specifically, a molecule structural formula of the liquid crystalvertical alignment molecules is

wherein R is

where m is an integer of 1-5 and n is an integer of 15-30; andpreferably, in is an integer of 2-4 and n is an integer of 16-24.

Specifically, by forming silicon-oxygen (Si—O) bonds with the graphene,the liquid crystal vertical alignment molecules graft on the graphenesurface.

Specifically, in this embodiment, the lower substrate 20 is the same asthe upper substrate 10, a side of the lower substrate 20 near the liquidcrystal layer 30 has a functionalized graphene layer 40 disposedthereon, a surface of a side of the functionalized graphene layer nearthe liquid crystal layer 30 has been rubbed, to provide apre-inclination angle for the liquid crystal molecules 31 in the liquidcrystal layer 30.

Specifically, the upper substrate 10 is a color film substrate, and thelower substrate 20 is a TFT array substrate.

Referring to FIG. 2, which schematically illustrates a structure of aliquid crystal panel containing functionalized graphene layer accordingto a second embodiment of the present application, in comparison withthe first embodiment, in this embodiment, the functionalized graphenelayer 40 is only disposed on the side of the upper substrate 10 near theliquid crystal 30, and an ITO electrode layer 51 and an alignment filmlayer 52 are successively bottom up disposed on the side of the lowersubstrate 20 near the liquid crystal layer 30, the alignment film layer52 provides a pre-inclination angle for the liquid crystal molecules 31in the liquid crystal layer 30.

In the liquid crystal panel structure containing a functionalizedgraphene layer of the present application, the functionalized graphenelayer thereof simultaneously plays effects of transparent conductivityand liquid crystal alignment, an alignment process that subsequentlyuses an alignment material is not necessary, the fabrication process andfilm structures of the liquid crystal panel are greatly simplified.

Referring to FIG. 3, the present application further provides a methodof preparing a functionalized graphene film, including following steps.

Step 1, functionalizing a graphene oxide: preparing a graphene oxide byutilizing Hummer's method; reacting the obtained graphene oxide withliquid crystal vertical alignment molecules having liquid crystalalignment function, to graft the vertical alignment molecules on asurface of the graphene oxide, to obtain a functionalized grapheneoxide.

Specifically, a molecule structural formula of the liquid crystalvertical alignment molecules is

wherein R is

where m is an integer of 1-5 and n is an integer of 15˜30; andpreferably, in is an integer of 2-4 and n is an integer of 16-24.

Specifically, as shown in FIG. 4, the liquid crystal vertical alignmentmolecules react with the graphene oxide, by forming silicon-oxygen(Si—O) bonds with the graphene oxide, the liquid crystal verticalalignment molecules graft on the graphene oxide surface, to obtain afunctionalized graphene oxide.

Step 2, forming a functionalized graphene oxide film: providing asolvent, mixing the functionalized graphene oxide obtained in Step 1with the solvent, and through a sonication, to obtain a uniformlydispersed functionalized graphene oxide dispersion; providing asubstrate, forming a functionalized graphene oxide film on the substrateby the functionalized graphene oxide dispersion.

Specifically, the solvent provided in Step 2 is a solvent of one ormixing more than one of acetonitrile, acetone, tetrahydrofuran,N-methylpyrrolidone, water, acetone, ethanol, N, N-dimethylformamide,dichloromethane, chloroform, propanol, isopropanol, and ethylene glycol.

Specifically, in Step 2, forming the functionalized graphene oxide filmon the substrate by the functionalized graphene oxide dispersion isperformed by a method of inkjet printing or transferring.

Preferably, in Step 2, forming the functionalized graphene oxide film onthe substrate by the functionalized graphene oxide dispersion isperformed by the method of inkjet printing.

Step 3, reducing the functionalized graphene oxide: performing ahydrogen gas reduction treatment to the functionalized graphene oxidefilm obtained in Step 2, to obtain a functionalized graphene film.

Specifically, as shown in FIG. 5, in Step 3, the hydrogen gas reductiontreatment performed to the functionalized graphene oxide allows carbonyl(—CO—), carboxyl (—CO) and hydroxyl (—COOH—) on the graphene oxide inthe functionalized graphene oxide be reduced, so as to provide moreexcellent conductivity and transparency to the graphene, wherein thegrafted vertical alignment molecule having alignment function cannot bereduced by the hydrogen gas, and they are retained on the graphenesurface.

Specifically, Step 3 further includes rubbing the obtainedfunctionalized graphene film, so as to play the function of providingthe pre-inclination angle for the liquid crystal molecules.

The method of preparing the functionalized graphene layer of the presentapplication sufficiently utilizes superiority of transparentconductivity of the graphene, and modifiability of the graphene surface,to endow the graphene with an effect of liquid crystal moleculealignment, the functionalized graphene layer prepared thereby hastransparency, conductivity and alignment functions, and it will alsoplay more obvious superiority in future flexible display and transparentdisplay.

In summary, in the liquid crystal panel structure containing afunctionalized graphene layer of the present application, thefunctionalized graphene layer thereof simultaneously plays effects oftransparent conductivity and liquid crystal alignment, an alignmentprocess that subsequently uses an alignment material is not necessary,the fabrication process and film structures of the liquid crystal panelare greatly simplified. In the method of preparing the functionalizedgraphene layer of the present application, the graphene oxide is firstlyprepared by Hummer's method, by reacting the liquid crystal verticalalignment molecules having liquid crystal alignment function withfunctional groups on the graphene surface, the functionalized grapheneoxide is obtained; then, the functionalized graphene oxide film isobtained by film-forming the functionalized graphene oxide; then otherfunctional groups containing oxygen on the functionalized graphene oxidefilm are reduced to obtain the material that is the functionalizedgraphene film of graphene surface grafted with liquid crystal verticalalignment molecules. The method of preparing the functionalized graphenelayer of the present application sufficiently utilizes superiority oftransparent conductivity of the graphene, and modifiability of thegraphene surface, to endow the graphene with an effect of liquid crystalmolecule alignment, the functionalized graphene layer prepared therebyhas transparency, conductivity and alignment function, and it will alsoplay more obvious superiority in future flexible display and transparentdisplay.

Based on the above description, an ordinarily skilled in the art cancomplete various similar modifications and arrangements according to thetechnical programs and ideas of the present application, and the scopeof the appended claims of the present application should encompass allsuch modifications and arrangements.

What is claimed is:
 1. A method for preparing a functionalized graphenefilm, comprising the following steps: Step 1, functionalizing a grapheneoxide: preparing a graphene oxide by utilizing Hummer's method, reactingthe obtained graphene oxide with liquid crystal vertical alignmentmolecules having liquid crystal alignment function, to graft thevertical alignment molecules on a surface of the graphene oxide, toobtain a functionalized graphene oxide; Step 2, forming a functionalizedgraphene oxide film: providing a solvent, mixing the functionalizedgraphene oxide obtained in Step 1 with the solvent, and through asonication, to obtain a uniformly dispersed functionalized grapheneoxide dispersion; providing a substrate, forming a functionalizedgraphene oxide film on the substrate by the functionalized grapheneoxide dispersion; Step 3, reducing the functionalized graphene oxide:performing a hydrogen gas reduction treatment to the functionalizedgraphene oxide film obtained in Step 2, to obtain a material that is afunctionalized graphene film of graphene surface grafted with liquidcrystal vertical alignment molecules; wherein a molecule structuralformula of the liquid crystal vertical alignment molecules is

 where R is one of

 m is an integer of 1-5; and n is an integer of 15-30.
 2. The methodaccording to claim 1, wherein the solvent provided in Step 2 is asolvent of one or a mixture of more than one of acetonitrile, acetone,tetrahydrofuran, N-methylpyrrolidone, water, acetone, ethanol, N,N-dimethylformamide, dichloromethane, chloroform, propanol, isopropanol,and ethylene glycol.
 3. The method according to claim 1, wherein Step 3further comprises rubbing the obtained functionalized graphene film. 4.The method according to claim 1, wherein in Step 2, forming thefunctionalized graphene oxide film on the substrate by thefunctionalized graphene oxide dispersion is performed by a method ofinkjet printing or transferring.
 5. A method for preparing afunctionalized graphene film, comprising the following steps: Step 1,functionalizing a graphene oxide: preparing a graphene oxide byutilizing Hummer's method, reacting the obtained graphene oxide withliquid crystal vertical alignment molecules having liquid crystalalignment function, to graft the vertical alignment molecules on asurface of the graphene oxide, to obtain a functionalized grapheneoxide; Step 2, forming a functionalized graphene oxide film: providing asolvent, mixing the functionalized graphene oxide obtained in Step 1with the solvent, and through a sonication, to obtain a uniformlydispersed functionalized graphene oxide dispersion; providing asubstrate, forming a functionalized graphene oxide film on the substrateby the functionalized graphene oxide dispersion; Step 3, reducing thefunctionalized graphene oxide: performing a hydrogen gas reductiontreatment to the functionalized graphene oxide film obtained in Step 2,to obtain a material that is a functionalized graphene film of graphenesurface grafted with liquid crystal vertical alignment molecules;wherein a molecule structural formula of the liquid crystal verticalalignment molecules is

 where R is one of

 m is an integer of 1-5; and n is an integer of 15-30; wherein thesolvent provided in Step 2 is a solvent of one or a mixture of more thanone of acetonitrile, acetone, tetrahydrofuran, N-methylpyrrolidone,water, acetone, ethanol, N, N-dimethylformamide, dichloromethane,chloroform, propanol, isopropanol, and ethylene glycol.
 6. The methodaccording to claim 5, wherein Step 3 further comprises rubbing theobtained functionalized graphene film.
 7. The method according to claim5, wherein in Step 2, forming the functionalized graphene oxide film onthe substrate by the functionalized graphene oxide dispersion isperformed by a method of inkjet printing or transferring.